Posterior predictive test of the four models. (Top) Visual illustration of the KS score, which measures the maximum difference between the eCDF of the observed flux ratios, ℛ_obs (plotted in black), and the eCDF of a simulated ℛ_obs distribution dependent on respectively the constant, log-normal, exponential, and bimodal model distribution of the escape fraction as inferred from the Bayesian framework. (Bottom) Residual (the model eCDF minus the data eCDF).